Mechanical stability and microstructural evolution during torsion in pristine and defect nickel nanowires of different orientations: a molecular dynamics simulation study

Abstract

ABSTRACT In the present study, torsional deformation behaviour and microstructural evolution in perfect and defect nickel nanowires (NWs) of different orientations is investigated. The studies are performed using molecular dynamics (MD) simulations. The torsion test is carried out at temperatures of 300 and 1200 K by applying a torque load of 0.02° ps−1. At the temperature of 300 K, the orientation NW yields at a higher torsional angle (θ [010] = 55.6°); than the NWs with ( = 39.8°) and (θ [111] = 48.8°) orientations. The orientation NW shows homogeneous plastic deformation by emitting coaxial dislocations throughout the length of the NW, whereas it is found to be heterogeneous in the other orientations. Twist boundaries are formed in [010] and in [111] orientations which are a rectangular array of dislocations in the former and a hexagonal array of dislocations in the latter orientations. Defects lower the torsional angle (critical) at which yielding occurs and is significant in the NWs when the defects are nearer to the surface. Furthermore, defect NWs are found to show pronounced strain localisation. The size effect studies show smaller is stronger, and the critical angle decreases with an increase in the temperature of deformation.